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In addition, an oxidation of the material can be carried out after nitriding in order to improve the corrosion resistance of the parts. A thin oxide Fe3O4(Magnetit)layer of 1-2 µm is formed. The surface becomes anthracite or even black. The post-oxidation is carried out as the last process step directly after nitriding.
After this step, no further treatment of the part should be performed. Depending on the shape of treated parts, a resistance of up to 300 h in the salt spray test can be reached after plasma nitriding and oxidation treatment. These treatment variants are applied for processing of parts which have to be both wear as corrosion resistant. Examples of such parts are gear spindles, hydraulic cylinders and various automotive parts.